Abstract

Despite a high concentration of serum proteins and intact phagocytes peritonitis exudates contain a large number of viable, pathogenic bacteria. The reason for this biological paradox is unknown. Our investigations reveal a pronounced defect in humoral opsonization of foreign particles in peritonitis exudate. We evaluated a modified chemiluminescence system allowing the determination of opsonic activity in serum and exudate. In serum we found a close correlation between opsonic activity and immunologically measurable levels of C3-complement and IgG. In purulent peritonitis exudates, however, the actual opsonizing activity was much less than expected according to the opsonin concentrations. We found a pronounced difference between immunologically determined opsonin levels and impaired opsonic function. Employing crossed immunoelectrophoresis massive C3-splitting into smaller fragments could be demonstrated in peritonitis exudates. In these exudates we found very high concentrations of granulocyte proteolytic (elastase) and oxidative (myeloperoxidase) enzymes which may lead to a functional destruction of opsonins followed by impaired opsonization in peritonitis exudate. The great number of bacteria and foreign particles in addition can cause a pronounced physiological consumption of complement components. The almost complete breakdown of intact C3-complement in intraabdominal exudate explains the deficient host defence in patients with severe peritonitis.